1. Field of the Invention
The present invention relates to a stop mechanism for stretch wrapping machines which stops the movement of the load or the packaging material dispenser in response to a stopping command or signal.
2. Description of the Related Art
Stretch wrapping machines wrap a web of packaging material around a load by providing relative rotation between a web dispenser and the load. These wrapping machines may be structured in various arrangements to accommodate particular applications. U.S. Pat. Nos. 3,793,798, 4,317,322, 4,302,920, 4,109,445, 4,722,170, 4,858,415, 4,845,920 and 4,866,909 are incorporated herein by reference to illustrate a number of these arrangements.
In U.S. Pat. No. 3,793,798, U.S. Pat. No. 4,109,445 and U.S. Pat. No. 4,722,170, a web dispenser is supported on an arm which extends radially outward and downward from a vertical axis. The arm moves the dispenser in an orbital path about the vertical axis to wrap the load. In U.S. Pat. No. 4,845,920 and U.S. Pat. No. 4,858,415 the load is placed on a rotatable turntable. As the turntable rotates about a vertical axis, the load is wrapped with a web which is dispensed from a dispenser. In U.S. Pat. No. 4,866,909, the wrapping machine has a rotatable annular frame which carries the web dispenser in an orbital path about a horizontal axis to wrap a load.
In each of these arrangements, either the web dispenser or the load support is a relatively heavy inertial body which travels at substantial velocities. While various braking devices have been used in some applications to stop the rotating body, there is a need for a reliable stopping system which stops the rotating support for the web dispenser or load in a minimal stopping distance after detection of an obstruction in its path or other condition such as an emergency stop or power loss.